So-called oxidation dyes are used for permanent, intensive colors with suitable fastness properties. Oxidation dyes typically consist of two components: one component typically includes oxidation dye precursors, so-called developer components and coupler components. The developer components form the actual dyes under the effect of oxidizing agents, in particular hydrogen peroxide, which are added to the first components only shortly before the application to hair, or of atmospheric oxygen with one another or with coupling with one or more coupler components. Primary aromatic amines with a further free or substituted hydroxy or amino group, in the para or ortho position, diaminopyridine derivatives, heterocyclic hydrazones, 4-aminopyrazolone derivatives and 2,4,5,6-tetraaminopyrimidine, and derivatives thereof are usually used as developer components. M-Phenylenediamine derivatives, naphthols, resorcinol, and resorcinol derivatives, pyrazolones, m-aminophenols, and substituted pyridine derivatives are normally used as coupler components. The oxidation dyes are characterized by excellent, long-lasting coloring results.
In order to stabilize the dye precursors during storage and to accelerate the reaction during the oxidative application, conventional oxidation dyes have a higher alkaline pH, which is far above 9.0 and is adjusted with alkalizing agents, such as alkanolamines, ammonia, or inorganic bases. Although in this regard ammonia in particular enables good coloring results, it also manifests disadvantages for the user due to its odor and irritation potential for skin and mucous membranes. The alkalizing agent results in the swelling of the keratinic fibers, as a result of which the dye precursors can easily penetrate into the hair. Nevertheless, the damaging action of the oxidizing agent on the hair structure is also intensified by the alkaline pH. For this reason, particular efforts focus on developing high-performance oxidation dyes, which have as low a pH as possible, therefore requiring only a low content of alkalizing agents, so that the damage to the hair structure by the oxidizing agent can be minimized.
Commercial oxidation dyes, in particular those sold at retail and used by the customer at home, are typically provided with standard directions for use, which recommend a specific application time for which the dye is to remain on the hair. This application time was determined by the manufacturer in extensive tests involving volunteers and is more likely based on subjects who have hair that is difficult to color or lighten and in whom the color absorbs onto the hair only after a rather long treatment time or the desired degree of lightening is achieved after a longer treatment time. Consumers with hair that is easy to color accordingly could definitely shorten the recommended standard application time and nevertheless achieve a good coloring or lightening result. In order to reduce the damage to the hair structure still further, it would be desirable therefore to limit the application time to the time after which the desired hair color was achieved. In order to realize this, it would be beneficial for the coloring component, as well as the application mixture, therefore the mixture of the color component and oxidizing agent, to be transparent.
Another requirement for oxidation dyes and/or lighteners is that the application mixture of the dye components and oxidizing agent component is sufficiently viscous, so that they can applied conveniently to hair and can remain there for the entire application time without any dripping or running.
The object of the present invention therefore was to provide oxidation dyes and/or lighteners for keratinic fibers, in particular hair, which cause as little hair damage as possible, in particular with good dyeing and/or lightening results, comparable to conventional highly alkaline dyes, and in particular with good absorption of the dyes on the keratinic fibers. A further object of the present invention was to provide transparent oxidation dyes and/or lighteners.
It was found surprisingly that oxidation dyes and/or lighteners, which are preferably transparent hydrogels and have a pH in the range of 7.0 to 8.8 and which preferably after mixing with an acidic oxidizing agent preparation produce an application mixture with a pH in the range of 6.0 to 7.3, enable intensive dyeing or lightening of the fibers, and nevertheless are associated with reduced hair damage.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.